1 Technical Field of the Invention
The present invention relates to a stator which has a stator core and a stator coil mounted on the stator core, and to a rotating electric machine which employs the stator.
2 Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2009-153367 discloses a technique for suppressing increase in size of a stator and preventing the performance of the stator from being lowered when the stator is used in a rotating electric machine.
Specifically, according to the technique, the stator has a stator core having a plurality of slots formed therein and a multi-phase stator coil comprised of a plurality of phase-windings. Each of the phase-windings is formed by serially connecting first and second windings wound on the stator core so that the winding direction of the phase-winding is reversed at a return portion between the first and second windings. Moreover, each of the phase-windings includes a plurality of in-slot portions, which are received in corresponding ones of the slots of the stator core, and a plurality of turn portions that connect adjacent pairs of the in-slot portions and are located alternately on opposite axial sides of the stator core. Furthermore, those of the turn portions which are located at the same circumferential position as that one of the turn portions which is immediately connected to one end of the return portion are radially shifted further, in a direction away from a rotor of the rotating electric machine, than the in-slot portions connected by the those turn portions.
However, from the above patent document, it is unclear whether the lengths of the phase-windings of the stator coil are equal to each other. Accordingly, it is also unclear whether the voltage drops across the phase-windings are equal to each other.
In addition, it is disclosed in the above patent document that the phase-windings are Y-connected (or star-connected) to form the stator coil. However, it is unclear whether the once Y-connected phase-windings can be disassembled and then reconnected into other connections (e.g., a Δ connection or a Y-Δ connection) for changing the inductance of the stator coil.